Fix memory leak in natives-external.

(Discovered when landing crrev.com/959693002)

R=jochen@chromium.org
BUG=

Review URL: https://codereview.chromium.org/960883003

Cr-Commit-Position: refs/heads/master@{#26889}

src/api.cc

@@ -5214,6 +5214,9 @@ void v8::V8::SetArrayBufferAllocator(
 
 bool v8::V8::Dispose() {
   i::V8::TearDown();
+#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+  i::DisposeNatives();
+#endif
   return true;
 }
 

src/natives-external.cc

@@ -132,6 +132,10 @@ class NativesHolder {
     DCHECK(store);
     holder_ = store;
   }
+  static void Dispose() {
+    DCHECK(holder_);
+    delete holder_;
+  }
 
  private:
   static NativesStore* holder_;
@@ -157,6 +161,15 @@ void SetNativesFromFile(StartupData* natives_blob) {
 }
 
 
+/**
+ * Release memory allocated by SetNativesFromFile.
+ */
+void DisposeNatives() {
+  NativesHolder<CORE>::Dispose();
+  NativesHolder<EXPERIMENTAL>::Dispose();
+}
+
+
 // Implement NativesCollection<T> bsaed on NativesHolder + NativesStore.
 //
 // (The callers expect a purely static interface, since this is how the

src/natives.h

@@ -40,6 +40,7 @@ typedef NativesCollection<EXPERIMENTAL> ExperimentalNatives;
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
 // Used for reading the natives at runtime. Implementation in natives-empty.cc
 void SetNativesFromFile(StartupData* natives_blob);
+void DisposeNatives();
 #endif
 
 } }  // namespace v8::internal

src/snapshot-empty.cc

@@ -19,6 +19,7 @@ namespace internal {
 // below. This happens when compiling the mksnapshot utility.
 void SetNativesFromFile(StartupData* data) { CHECK(false); }
 void SetSnapshotFromFile(StartupData* data) { CHECK(false); }
+void DisposeNatives() {}
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA